Heretofore, a front bumper provided with an energy absorber on a front side of its bumper reinforcement has been known. A front face of the energy absorber is formed into an arc shape in a plan view, so that when the vehicle causes a frontal crash, a central portion of the energy absorber in a vehicle width direction is compressively deformed most largely, and the compressive deformation amount decreases at end portions thereof in the vehicle width direction. Hence, to equalize the amount of impact energy to be absorbed along the entire vehicle width direction, there is developed a bumper provided with an energy absorber whose sectional area gradually increases toward a central portion thereof in the vehicle width direction (see Patent Document 1, for example).